Targeting CD40-Induced TRAF6 Signaling in Macrophages Reduces Atherosclerosis

Abstract

BackgroundDisrupting the costimulatory CD40-CD40L dyad reduces atherosclerosis, but can result in immune suppression. The authors recently identified small molecule inhibitors that block the interaction between CD40 and tumor necrosis factor receptor-associated factor (TRAF) 6 (TRAF-STOPs), while leaving CD40-TRAF2/3/5 interactions intact, thereby preserving CD40-mediated immunity.ObjectivesThis study evaluates the potential of TRAF-STOP treatment in atherosclerosis.MethodsThe effects of TRAF-STOPs on atherosclerosis were investigated in apolipoprotein E deficient (Apoe−/−) mice. Recombinant high-density lipoprotein (rHDL) nanoparticles were used to target TRAF-STOPs to macrophages.ResultsTRAF-STOP treatment of young Apoe−/− mice reduced atherosclerosis by reducing CD40 and integrin expression in classical monocytes, thereby hampering monocyte recruitment. When Apoe−/− mice with established atherosclerosis were treated with TRAF-STOPs, plaque progression was halted, and plaques contained an increase in collagen, developed small necrotic cores, and contained only a few immune cells. TRAF-STOP treatment did not impair “classical” immune pathways of CD40, including T-cell proliferation and costimulation, Ig isotype switching, or germinal center formation, but reduced CD40 and β2-integrin expression in inflammatory monocytes. In vitro testing and transcriptional profiling showed that TRAF-STOPs are effective in reducing macrophage migration and activation, which could be attributed to reduced phosphorylation of signaling intermediates of the canonical NF-κB pathway. To target TRAF-STOPs specifically to macrophages, TRAF-STOP 6877002 was incorporated into rHDL nanoparticles. Six weeks of rHDL-6877002 treatment attenuated the initiation of atherosclerosis in Apoe−/− mice.ConclusionsTRAF-STOPs can overcome the current limitations of long-term CD40 inhibition in atherosclerosis and have the potential to become a future therapeutic for atherosclerosis.

Profiling of immune‐related gene expression in children with familial hypercholesterolaemia

“…Pathways activated through CD40 or BAFFR via TRAF1/2/3/5/6 may subsequently activate mitogen-activated protein kinases or trigger BCL2 transcription, respectively, in B cells [25]. Regarding prevention of atherosclerosis, targeting TRAF6 through CD40 has drawn attention [26], but enhanced expression of TRAF1/2/3/ 5 in human atherosclerotic plaques also indicate a role of these TRAF members in atherosclerosis [27]. We found higher expression of BAFFR (TNFRSF13C), TRAF1/3/5, MAP4K2 and BCL2 in children with FH, possibly suggesting LDL-C-induced activation of several TRAF members and pathways in PBMCs, and again, some of these could be targeted therapeutically [26].…”

Macrophage CD40 signaling drives experimental autoimmune encephalomyelitis

“…However, the reduction in neuroinflammation was stronger in mice lacking CD40–TRAF6 signaling in all MHCII + cells than in mice lacking CD40 signaling in macrophages, suggesting that both CD40–TRAF6 signaling in macrophages and other antigen‐presenting cells including B cells and dendritic cells drive neuroinflammation. Recently, we have developed small molecule inhibitors of the CD40–TRAF6 interaction, TRAF‐STOPs, and we were able to show that these small molecule inhibitors can reduce atherosclerosis, peritonitis, sepsis and metabolic complications of diet‐induced obesity in mice . Interestingly, TRAF‐STOP treatment was also able to reduce CNS leukocyte infiltration during EAE in both mice and rats but unfortunately failed to ameliorate disease severity .…”

Cancer patients receiving immune checkpoint inhibitor therapy are at an increased risk for atherosclerotic cardiovascular disease

“…Atherosclerosis is a chronic lipid-driven inflammatory disease that results in the formation of lipid-rich and immune cellrich plaques in the arterial wall. 2 During the progression of atherosclerosis, these lesions may rupture, which results in thrombus formation and subsequent vascular occlusion. 2 Single-cell RNA sequencing as well as mass cytometry of human atherosclerotic plaques recently demonstrated that T cells are a dominant immune cell type in human atherosclerotic lesions.…”

“…2 During the progression of atherosclerosis, these lesions may rupture, which results in thrombus formation and subsequent vascular occlusion. 2 Single-cell RNA sequencing as well as mass cytometry of human atherosclerotic plaques recently demonstrated that T cells are a dominant immune cell type in human atherosclerotic lesions. 3 Both CD4 + and CD8 + T cells in the plaque display an activated profile, which will not only promote the initiation of atherosclerotic lesion formation but also drives the progression towards vulnerable plaques that may trigger myocardial infarction or ischemic stroke on rupture.…”

“…2 3 It is well known that immune checkpoint proteins orchestrate the inflammatory response that underlies atherogenesis and preclinical studies have elucidated the role of the ICI targets cytotoxic T-lymphocyte associated protein 4 (CTLA4) and programmed cell death protein 1 (PD1) in atherosclerosis. 2 For example, T cell-specific overexpression of CTLA4 reduces atherosclerotic lesion formation in apolipoprotein E deficient mice and limits plaque inflammation, as reflected by decreased CD4 + T cells and macrophage abundance. 2 While CTLA4 overexpression reduced systemic regulatory T cell numbers, the suppressive capacity of these cells increased and CD4 + T cell proliferation, activation, and cytokine production was Open access reduced, resulting in an atheroprotective T cell profile in hyperlipidemic mice.…”